This invention relates generally to radiographic inspection system, and more particularly to a method of aligning a radiographic source with a detector.
Radiographic apparatus, particularly X-ray apparatus, is used to measure or inspect an object for the purposes of evaluating its characteristics. Radiation projected by a source is absorbed to varying degrees by the inspected object, depending on its size, mass, and configuration. The photons that continue through the object are counted or measured by a detector, and the pattern of flux variation across the object provides information about it. To obtain an optimum image, the X-Ray source, detector, and inspected object must be aligned. Small improvements in this alignment can often provide significant improvement in image quality.
Because X-Rays are ionizing radiation and dangerous to humans, means are required to prevent or minimize personnel exposure. This is accomplished by designating areas of danger and excluding personnel from them, or by creating X-Ray absorbing structures to contain the X-Rays within a reduced area. In the inspection of smaller objects, the objects themselves can be taken to a location containing a shielded and permanently aligned inspection system. For larger objects, such as aircraft fuselages and gas turbine engine components, however, the X-Ray inspection system must be taken to the object, and there assembled and aligned. Depending on the size and configuration of the object and system, the detector and X-Ray tube may not be within line of sight of each other, or even be seen from a single separate location, making alignment of the source, detector, and shielding difficult
Prior art X-ray tubes, detectors, and shielding are typically aligned using expensive fixtures, jigs and external sensors, or by approximation and iteration. Images are taken, evaluated, and the system's alignment changed. For inspection of large objects, this is often difficult, slow, and can result in unnecessary exposure to X-Rays. Additionally, sub-optimal images are produced unless the alignment is proper.
Accordingly, there is a need for a method of aligning a radiographic system where a line-of-sight is not available between the source and the detector